Advances in semiconductor processing and logic design have permitted an increase in the amount of logic that may be present on integrated circuit devices. As a result, computer system configurations have evolved from a single or multiple integrated circuits in a system to multiple hardware threads, multiple cores, multiple devices, and/or complete systems on individual integrated circuits. Additionally, as the density of integrated circuits has grown, the power requirements for computing systems (from embedded systems to servers) have also escalated. Furthermore, software inefficiencies, and its requirements of hardware, have also caused an increase in computing device energy consumption. In fact, some studies indicate that computing devices consume a sizeable percentage of the entire electricity supply for a country, such as the United States of America. As a result, there is a vital need for energy efficiency and conservation associated with integrated circuits. These needs will increase as servers, desktop computers, notebooks, Ultrabooks™, tablets, mobile phones, processors, embedded systems, etc. become even more prevalent (from inclusion in the typical computer, automobiles, and televisions to biotechnology). Power consumption limitations may be enforced in a given system to ensure that it complies with its power requirements to operate in a given environment (and within its cooling system).
Radiation-induced soft errors, caused primarily by neutron particles, have become a problem for processor designers. Because this type of error does not reflect a permanent failure of the device, it is termed a soft or transient error. These bit upsets from transient faults are in addition to those caused by alpha particles from packaging material and bumps. As the number of transistors on a single chip increases and voltage scaling continues, such soft errors are expected to increase. To address this concern, processors often include some form of error detection and/or recovery. Nonetheless, as more transistors are added to a single chip it becomes even more challenging to maintain the same level of reliability in succeeding generations of processors.